libct/cg: rm "unsupported.go" files

These are not needed as these packages (libcontainer/cgroups,
libcontainer/cgroups/fs, and libcontainer/cgroups/systemd) can
not be built under non-linux anyway (for various reasons).

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

libcontainer/cgroups/cgroups_unsupported.go

@@ -1,3 +0,0 @@
-// +build !linux
-
-package cgroups

libcontainer/cgroups/fs/unsupported.go

@@ -1,3 +0,0 @@
-// +build !linux
-
-package fs

libcontainer/cgroups/systemd/unsupported.go

@@ -1,71 +0,0 @@
-// +build !linux
-
-package systemd
-
-import (
-	"errors"
-
-	"github.com/opencontainers/runc/libcontainer/cgroups"
-	"github.com/opencontainers/runc/libcontainer/configs"
-)
-
-type Manager struct {
-	Cgroups *configs.Cgroup
-	Paths   map[string]string
-}
-
-func IsRunningSystemd() bool {
-	return false
-}
-
-func NewSystemdCgroupsManager() (func(config *configs.Cgroup, paths map[string]string) cgroups.Manager, error) {
-	return nil, errors.New("Systemd not supported")
-}
-
-func (m *Manager) Apply(pid int) error {
-	return errors.New("Systemd not supported")
-}
-
-func (m *Manager) GetPids() ([]int, error) {
-	return nil, errors.New("Systemd not supported")
-}
-
-func (m *Manager) GetAllPids() ([]int, error) {
-	return nil, errors.New("Systemd not supported")
-}
-
-func (m *Manager) Destroy() error {
-	return errors.New("Systemd not supported")
-}
-
-func (m *Manager) GetPaths() map[string]string {
-	return nil
-}
-
-func (m *Manager) Path(_ string) string {
-	return ""
-}
-
-func (m *Manager) GetStats() (*cgroups.Stats, error) {
-	return nil, errors.New("Systemd not supported")
-}
-
-func (m *Manager) Set(container *configs.Config) error {
-	return errors.New("Systemd not supported")
-}
-
-func (m *Manager) Freeze(state configs.FreezerState) error {
-	return errors.New("Systemd not supported")
-}
-
-func Freeze(c *configs.Cgroup, state configs.FreezerState) error {
-	return errors.New("Systemd not supported")
-}
-
-func (m *Manager) GetCgroups() (*configs.Cgroup, error) {
-	return nil, errors.New("Systemd not supported")
-}
-
-func (m *Manager) Exists() bool {
-	return false
-}